The present invention relates to a projection-type television, and more particularly to a projection-type television having a movable reflective mirror between a screen and a projection tube for projecting images.
In accordance with the coming of the information age, together with the appearance of various information transferring media, the size of image display devices needs to be increased. However, a conventional cathode ray tube (CRT) does not meet such requirements.
In other words, since current technology is limited in fabrication of large-scale conventional CRTs, the images from a small-sized CRT or a liquid crystal light valve, etc. are enlarged using an optical lens, to obtain a large-scale picture.
Projection methods are classified into a front projection method whereby enlarged images are projected on the front surface of a screen, and a rear projection method in which the enlarged images are projected onto the rear surface of a transmission-type screen. In view of image brightness, the rear projection method is much more advantageous.
In the case of a rear projection method as shown in FIG. 1, a necessary overall focus distance should be ensured to get a large-scale picture screen which has been determined in view of the optical design. Also, the depth of a cabinet 20 is designed while taking external aesthetics into consideration, and thus a method of redirecting an optical axis using a reflective mirror 21 is adopted.
With respect to the product's outward appearance, generally, only a portion of reflective mirror 21 protrudes outwardly, so that the depth of the product seems shallow. In this case, as the actual depth of the product does not change, the necessary packing volume remains unchanged. Nevertheless, the product is difficult to pack due to the protruding reflective mirror.
To overcome such drawbacks, the screen and the reflective mirror may be connected with a plurality of hinged crank rods which can be operated so as to move a screen and mirror assembly inside the cabinet. This is disclosed in U.S. Pat. No. 4,647,166. However, such a structure is complicated and, when the screen is in the operational position, the portion thereof which protrudes forwardly lends to an ungainly product appearance.